I debugged my Problem once again and checked the edit_info-structure.
The program runs fine, when I increase the size of the structure, by defining the last entry ("reserved") as an Array. I can see, that the first 8 items of the integer*2-array "reserved" are changed when %eb is called. So I changed the type structure of edit_info to:

I replaced the DLLs with the new ones but have still the same program crash (Access Violation), no matter if I compile it with /debug or not, or using sdbg64 or not.
Funnily enough the contents of the 32byte that are written on info_eb%reserved is four times "BAADF00D", when displaying it in hexadecimal.
For completeness, here are my makefiles:

I don't know, if it makes any difference, but my OS is Windows 10 Enterprice, Version 1709.
Do you think that there may be any disadvantage, if I extend the type structure in the way I explained before?

There should be no problem when you increase the size of TYPE edit_info. It just has to be a block of memory large enough for the internal workings of ClearWin+.

If you want to access the information from your program then you will need to know the offset from the beginning of the structure to the information you need. Otherwise you could go back to using an integer array provided its size is increased to accommodate the new INTEGER*8 addresses.

There is no explicit reference to "reserved" in the ClearWin+ code so at the moment the fault remains unexplained.